Support for dynamically loadable and unloadable protocols within existing protocol

families.

The protosw[] array of any particular protocol family ("domain") is of fixed size
defined at compile time.  This made it impossible to dynamically add or remove any
protocols to or from it.  We work around this by introducing so called SPACER's
which are embedded into the protosw[] array at compile time.  The SPACER's have
a special protocol number (32767) to indicate the fact that they are SPACER's but
are otherwise NULL.  Only as many protocols can be dynamically loaded as SPACER's
are provided in the protosw[] structure.

The pr_usrreqs structure is treated more special and contains pointers to dummy
functions only returning EOPNOTSUPP.  This is needed because the use of those
functions pointers is usually not checked within the kernel because until now it
was assumed to be a valid function pointer.  Instead of fixing all potential
callers we just return a proper error code.

Two new functions provide a clean API to register and unregister a protocol.  The
register function expects a pointer to a valid and complete struct protosw including
a pointer to struct pru_usrreqs provided by the caller.  Upon successful registration
the pr_init() function will be called to finish initialization of the protocol.  The
unregister function restores the SPACER in place of the protocol again.  It is the
responseability of the caller to ensure proper closing of all sockets and freeing
of memory allocation by the unloading protocol.

 sys/protosw.h

  o Define generic PROTO_SPACER to be 32767
  o Prototypes for all pru_*_notsupp() functions
  o Prototypes for pf_proto_[un]register() functions

 kern/uipc_domain.c

  o Global struct pr_usrreqs nousrreqs containing valid pointers to the
    pru_*_notsupp() functions
  o New functions pf_proto_[un]register()

 kern/uipc_socket2.c

  o New functions bodies for all pru_*_notsupp() functions

1 files changed, 33 insertions, 0 deletions

diff --git a/sys/sys/protosw.h b/sys/sys/protosw.h
index 617ab59..f4bb734 100644
--- a/sys/sys/protosw.h
+++ b/sys/sys/protosw.h
@@ -105,6 +105,12 @@ struct protosw {
 #define	PR_FASTHZ	5		/* 5 fast timeouts per second */
 
 /*
+ * This number should be defined again within each protocol family to avoid
+ * confusion.
+ */
+#define	PROTO_SPACER	32767		/* spacer for loadable protocols */
+
+/*
  * Values for pr_flags.
  * PR_ADDR requires PR_ATOMIC;
  * PR_ADDR and PR_CONNREQUIRED are mutually exclusive.
@@ -231,16 +237,41 @@ struct pr_usrreqs {
 	void	(*pru_sosetlabel)(struct socket *so);
 };
 
+/*
+ * The dummy protocol specific user requests function pointer array is
+ * initialized to the functions below.  All functions return EOPNOTSUPP.
+ */
+extern	struct pr_usrreqs nousrreqs;
+
+int	pru_abort_notsupp(struct socket *so);
 int	pru_accept_notsupp(struct socket *so, struct sockaddr **nam);
+int	pru_attach_notsupp(struct socket *so, int proto, struct thread *td);
+int	pru_bind_notsupp(struct socket *so, struct sockaddr *nam,
+	    struct thread *td);
 int	pru_connect_notsupp(struct socket *so, struct sockaddr *nam,
 	    struct thread *td);
 int	pru_connect2_notsupp(struct socket *so1, struct socket *so2);
 int	pru_control_notsupp(struct socket *so, u_long cmd, caddr_t data,
 	    struct ifnet *ifp, struct thread *td);
+int	pru_detach_notsupp(struct socket *so);
+int	pru_disconnect_notsupp(struct socket *so);
 int	pru_listen_notsupp(struct socket *so, struct thread *td);
+int	pru_peeraddr_notsupp(struct socket *so, struct sockaddr **nam);
 int	pru_rcvd_notsupp(struct socket *so, int flags);
 int	pru_rcvoob_notsupp(struct socket *so, struct mbuf *m, int flags);
+int	pru_send_notsupp(struct socket *so, int flags, struct mbuf *m,
+	    struct sockaddr *addr, struct mbuf *control, struct thread *td);
 int	pru_sense_null(struct socket *so, struct stat *sb);
+int	pru_shutdown_notsupp(struct socket *so);
+int	pru_sockaddr_notsupp(struct socket *so, struct sockaddr **nam);
+int	pru_sosend_notsupp(struct socket *so, struct sockaddr *addr,
+	    struct uio *uio, struct mbuf *top, struct mbuf *control, int flags,
+	    struct thread *td);
+int	pru_soreceive_notsupp(struct socket *so, struct sockaddr **paddr,
+	    struct uio *uio, struct mbuf **mp0, struct mbuf **controlp,
+	    int *flagsp);
+int	pru_sopoll_notsupp(struct socket *so, int events, struct ucred *cred,
+	    struct thread *td);
 void	pru_sosetlabel_null(struct socket *so);
 
 #endif /* _KERNEL */
@@ -319,6 +350,8 @@ void	pfctlinput(int, struct sockaddr *);
 void	pfctlinput2(int, struct sockaddr *, void *);
 struct protosw *pffindproto(int family, int protocol, int type);
 struct protosw *pffindtype(int family, int type);
+int	pf_proto_register(int family, struct protosw *npr);
+int	pf_proto_unregister(int family, int protocol, int type);
 #endif
 
 #endif